High brightness wide gamut display

ABSTRACT

A device to produce a color image, the device including a color filtering arrangement to produce at least four colors, each color produced by a filter on a color filtering mechanism having a relative segment size, wherein the relative segment sizes of at least two of the primary colors differ.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/272,850, filed Nov. 18, 2008, which is acontinuation application of U.S. patent application Ser. No. 10/491,726,filed Apr. 5, 2004, which is a National Phase Application of PCTInternational Application No. PCT/IL2003/000610, entitled “HIGHBRIGHTNESS WIDE GAMUT DISPLAY”, International Filing Date Jul. 24, 2003,published on Jan. 29, 2004 as International Publication No. WO2004/010407, which in turn claims priority from U.S. Provisional PatentApplication No. 60/397,781, filed Jul. 24, 2002, all of which areincorporated herein by reference in their entirety

FIELD OF THE INVENTION

The invention relates generally to color display devices and methods ofdisplaying color images and, more particularly, to high brightnessand/or wide color gamut displays.

BACKGROUND

Various types of color display technologies are known in the art. Forexample, there are CRT display systems, LCD systems, and projectiondisplay systems. In front projection displays, the projected images areviewed from a reflective viewing screen. In rear projection displays,the projected images are viewed through a transmissive viewing screen.

To produce color images, existing display devices use three primarycolors, typically, red green and blue, collectively referred to as RGB.In sequential projection display systems, the three primary colorcomponents of an image are modulated and displayed sequentially,typically using a single Spatial Light Modulator (SLM) panel. Insimultaneous projection display systems, the three primary colorcomponents of the image are modulated and displayed simultaneously usingone or more SLM panels.

An important consideration in designing projection display devices isthe display brightness. Thus, efforts are continually made to increasethe optical efficiency of existing designs and, thereby, to increase theluminous output that can be obtained from a given light source.

Unfortunately, the light sources commonly used in existing displaydevices, for example, the UHP™ lamps available from Philips Lighting, adivision of Royal Philips Electronics, Eindhoven, Netherlands, producenon-uniform light spectra wherein, typically, the intensity of the redwavelength range is significantly lower than the intensity of otherspectral ranges. Thus, in existing RGB systems, typically, higherbrightness may be achieved only by significantly reducing the colorsaturation of the red wavelength ranges. Further, in projection displaysystems for home theater applications, wherein highly saturated colorsare typically required, filters with narrower spectral transmissionranges are typically used, causing an additional reduction in imagebrightness.

The quality of color image reproduction can be significantly improved byexpanding the color gamut of the display system. This can be achieved byusing more than three primary colors to reproduce the image. Displaysystems using more than three primary colors are described inInternational Application PCT/IL01/00527, entitled “Device, System andMethod For Electronic True Color Display”, filed Jun. 7, 2001, andpublished Dec. 13, 2001 as WO 01/95544, assigned to the assignee of thepresent application, the entire disclosure of which is incorporatedherein by reference.

A six-primary display using superimposed images produced by twoprojection display devices, wherein each projection display device usesthree different primary colors, is described in Masahiro Yamaguchi,Taishi Teraji, Kenro Ohsawa, Toshio Uchiyama, Hideto Motomura YuriMurakami, and Nagaaki Ohyama, “Color image reproduction based on themultispectral and multiprimary imaging: Experimental evaluation”, DeviceIndependent Color, Color Hardcopy and Applications VII, Proc. SPIE, Vol.4663, pp. 15-26 (2002). In the dual-projection display system describedin this reference, the wavelength ranges selected for the six primarycolor filters are essentially uniformly distributed across the visiblespectra of 400-700 nm, with no spectral overlap between the primaries.In this way, a wide gamut may be achieved; however, the combinedbrightness of the two projection devices is dramatically reduced. Infact, the combined brightness produced by this dual-projection device islower than the brightness produced by a corresponding single RGBprojection device. Dividing the visible spectrum into six (rather thanthree) ranges does not increase the over-all image brightness becausethe six primaries cover narrower sub-ranges of the same visiblespectrum. An additional reduction of intensity is caused by inherentoptical losses in the division of the spectrum into narrower ranges.

SUMMARY OF EMBODIMENTS OF THE INVENTION

An embodiment of the present invention provides a multi-primary colordisplay device, e.g., a color projection display device, which producesimages having a wide color gamut at brightness levels significantlyhigher than those of prior art devices. Further, for a given lightsource, the brightness level produced by embodiments of the device ofthe present invention is at least equal, and in some cases higher, thanthe brightness level of a conventional RGB projection display deviceusing the same light source.

Embodiments of the present invention increase the efficiency of displaydevices by utilizing a relatively large portion of the polychromaticlight generated by a light source, compared to conventional devices,while maintaining a relatively wide color gamut of the displayed images.According to embodiments of the invention, n primaries, wherein n isgreater than three, may be selected and used to utilize some or all ofthe conventionally unused part of the white light generated by the lightsource, in order to provide increased brightness and/or a wider colorgamut.

According to some of these embodiments, an increase in illuminationefficiency may be achieved by using partially overlapping primary colorspectra, wherein at least two of the primary color spectra overlapsignificantly. A specifically designed color filtering arrangement, e.g.including sets of filters or other filtering elements, may be used toconvert white light into the desired, significantly overlapping spectra.The significantly overlapping primary color spectra may allow a largerpercentage of the white light generated by the light source to beutilized by the display device. For example, when the device of theinvention is operated in “full illumination” mode, i.e., when all theprimary colors are at their maximum levels, the wide color gamut deviceof the invention may produce a white light output at levels comparableto, or even higher than, those of produced by a corresponding RGBprojection device having a much narrower color gamut.

Further, specific designs of the filtering elements and overlap rangesof the wide gamut display of the invention may compensate fornon-uniformities and other deficiencies of the light spectra generatedby the white light source. In embodiments of the invention, thetransmission curves of the filtering elements may be designedspecifically to maximize the display brightness for a given color gamut,whereby substantially all colors within the desired color gamut may bereproduced at optimal efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood and appreciated more fully from thefollowing detailed description of embodiments of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1A is a schematic illustration of the spectral output of ahigh-pressure mercury lamp in accordance with exemplary embodiments ofthe invention;

FIG. 1B is a schematic illustration of the spectral output of a Xenonlight source in accordance with further exemplary embodiments of theinvention;

FIG. 2 is a schematic illustration of an optical configuration for adevice, in accordance with exemplary embodiments of the invention;

FIGS. 3A and 3B are schematic illustrations of primary color wavelengthspectra for a six-primary color display using the configuration of FIG.2, in accordance with exemplary embodiments of the invention;

FIG. 4 is a schematic illustration of the color gamut resulting from theprimary color spectra of FIGS. 3A and 3B;

FIG. 5 is a schematic illustration of primary color wavelength spectrafor a five-primary color display in accordance with one exemplaryembodiment of the invention;

FIG. 6 is a schematic illustration of the color gamut resulting from theprimary color spectra of FIG. 5;

FIG. 7 is a schematic illustration of primary color wavelength spectrafor a five-primary color display in accordance with another exemplaryembodiment of the invention;

FIG. 8 is a schematic illustration of the color gamut resulting from theprimary color spectra of FIG. 7;

FIG. 9 is a schematic illustration of primary color wavelength spectrafor a four-primary color display in accordance with one exemplaryembodiment of the invention;

FIG. 10 is a schematic illustration of the color gamut resulting fromthe primary color spectra of FIG. 9;

FIG. 11 is a schematic illustration of primary color wavelength spectrafor a four-primary color display in accordance with another exemplaryembodiment of the invention;

FIG. 12 is a schematic illustration of the color gamut resulting fromthe primary color spectra of FIG. 11; and

FIG. 13 is a schematic illustration of a color switching mechanismaccording to some exemplary embodiments of the invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn accuratelyor to scale. For example, the dimensions of some of the elements may beexaggerated relative to other elements for clarity or several physicalcomponents included in one element. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements. It will be appreciatedthat these figures present examples of embodiments of the presentinvention and are not intended to limit the scope of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following description, various aspects of the present inventionwill be described. For purposes of explanation, specific configurationsand details are set forth in order to provide a thorough understandingof the present invention. However, it will be apparent to one skilled inthe art that the present invention may be practiced without the specificdetails presented herein. Furthermore, some features of the inventionrelying on principles and implementations known in the art may beomitted or simplified to avoid obscuring the present invention.

The following description of exemplary embodiments of the invention isbased on a projection display system using a high-pressure mercury lamp,e.g., the UHP™ 100 Watt lamp, available from Philips Lighting, adivision of Royal Philips Electronics, Eindhoven, Netherlands, or anyother suitable white light source having a similar spectral range. FIG.1A schematically illustrates the spectral output of the high-pressuremercury UHP™ 100 Watt lamp. It will be appreciated that all other typesof high-pressure mercury lamps, such as the VIP lamp available fromOsram, Berlin, Germany, have similar spectra and similar designs, so thefollowing examples apply to all such lamps.

The examples herein are described in the context of high-pressuremercury type lamps because such lamps are most commonly used inprojection display devices. However, some aspects of the embodimentsdescribed herein, e.g., the use of significantly overlapping primarycolor spectral ranges, may be applied in designing color filteringarrangements for other devices using other types of light sources. Forexample, aspects of the invention may be applied to devices using Xenon(Xe) type light sources, as are known in the art, having a spectraloutput as illustrated schematically in FIG. 1B. It will be appreciatedby persons skilled in the art that the output spectra of the Xe typelamp of FIG. 1B is much smoother, and thus less difficult toaccommodate, for the purpose of designing partially-overlapping spectrain accordance with embodiments of the invention, than the relatively“peaky” output spectra of the mercury type lamp of FIG. 1A.

For simplicity, the following description ignores possiblenon-uniformities in the spectral transmission properties of the opticalelements used by the device of the invention. It will be appreciated,however, that such non-uniformities are not significant.

By appropriately selecting a desired set of partially overlappingprimary colors, and by appropriately designing a color filteringarrangement to produce such primary colors, the method and device of thefollowing exemplary embodiments of the invention may be implemented inconjunction with any color display system known in the art. In someembodiments of the invention, the display system may use more thanthree, partially overlapping primary colors. Display systems using morethan three primary colors are described in International ApplicationPCT/IL01/00527, entitled “Device, System and Method For Electronic TrueColor Display”, filed Jun. 7, 2001, published Dec. 13, 2001 as WO01/95544, and in International Application PCT/IL01/01179, entitled“Spectrally Matched Print Proofer”, filed Dec. 18, 2001, published Jun.27, 2002 as WO 02/50763, assigned to the assignee of the presentapplication, the entire disclosure of both of which is incorporatedherein by reference.

Example 1 Six Primaries, Six-Panel Wide Gamut Display

The following example illustrates selection of primary color wavelengthranges for a wide gamut display using six Spatial Light Modulator (SLM)panels, wherein each panel produces one primary color. Thisconfiguration may allow full coverage of the typical color gamut of aprojection film, e.g., a motion picture positive film, enabling aprojection display to produce virtually all the colors that can beproduced by projection film, as described below. FIG. 2 schematicallyillustrates an optical configuration of a device in accordance with thisembodiment of the invention. The exemplary configuration of FIG. 2 isparticularly adapted for devices using reflective-LCD type SLM panels.

According to embodiments of the invention, light from an illuminationunit 201, which may include any suitable white light source known in theart, as described above, may be imaged onto LCD panels 206, 207, 208,209, 210 and 211, via a relay lens 202, a reflection-transmissionelement, e.g., a polarizing beam splitter (PBS) 203, and a colorseparation arrangement, e.g., “X” color-separator cubes 204 and 205.Each of LCD panels 206, 207, 208, 209, 210 and 211 may include an arrayof pixels, as is known in the art, which may be selectively activated toproduce a reflective pattern corresponding to one of a plurality ofprimary color images. In the example described herein, each LCD panelmay be separately activated by a control unit (not shown in thedrawings) to produce a reflective pattern corresponding to one of sixindependent primary color images, in accordance with an input signalrepresenting a six-primary-color image. Such an input signal may begenerated using any of the methods described in the above-referencedInternational Patent Applications, e.g., by converting athree-primary-color image signal into a six-primary-color image signal.As described below, each reflective pattern may modulate a correspondingprimary color light beam to produce a corresponding primary color imagecomponent.

PBS 203 may split the white light from unit 201 into a reflected“s”-polarized component and a transmitted “p”-polarized component, as isknown in the art. The “s”-polarized component may be separated by “X”color separation cube 204 into light beams of three different wavelengthranges, which correspond to three of the six primaries used in thisembodiment of the invention. The operation of “X”-cubes as multiplefiltering elements for color separation is well known in the art andcommercially available. An example of such commercially availablecomponent is the Optec™ Standard Cubic Dichroic (X-Cube) Beam-splitteravailable from Richter Enterprises, Texas, United States.

It may be appreciated by those skilled in the art that any othersuitable color filtering arrangement may be used, for example, toimplement a desired number of primary colors. For example, the colorfiltering arrangement may include one “X” color separation cube and adichroic mirror, as are known in the art, to separate the polarizedcomponents into five primary color light beams.

Each pixel of LCD panels 206, 207 and 208, when activated to an “on”state, may convert the “s”-polarized light into corresponding“p”-polarized light, as is known in the art, and may reflect theconverted light back via “X” color separation cube 204. The threeprimary color light beams exiting “X”-cube 204, which beams aremodulated in accordance with three, respective, primary color imagecomponents, may be transmitted through PBS 203 towards projection lens212. Analogously, the transmitted “p”-polarized light may be separatedby “X” color separation cube 205 into three different color light beams,corresponding to the remaining three primary colors. Each pixel of LCDpanels 209, 210 and 211, when activated to an “on” state, may convertthe “p”-polarized light into corresponding “s”-polarized light, as isknown in the art, and may reflect the converted light back via “X” colorseparation cube 205. The three color light beams exiting “X”-cube 205,which beams are modulated in accordance with three, respective, primarycolor image components, may be deflected by PBS 203 towards projectionlens 212. The projection lens may project all six modulated coloredlight beams, i.e., all six primary color image components, onto aviewing screen (not shown in the drawings).

It should be noted that the separate wavelength ranges produced by“X”-cube devices are inherently non-overlapping. Therefore, in theexample described herein, there is no spectral overlap among the threeprimary color spectra produced by each “X”-cube, 204 or 205. Therefore,in this configuration, the desired partial overlap between primary colorspectra, in accordance with embodiments of the invention, may beachieved by overlaps between the primary color spectra produced by“X”-cube 204 and the primary color spectra produced by “X”-cube 205. Itwill be appreciated by persons skilled in the art that essentially anydesired overlapping can be achieved between primary color spectraproduced by two “X”-cubes.

FIGS. 3A and 3B schematically illustrate primary color wavelengthspectra for a six-primary color display using the configuration of FIG.2. FIG. 3A shows the wavelength spectra of a set of threenon-overlapping primary colors having spectral ranges of approximately400-500 nm, approximately 500-550 nm, and approximately 575-750 nm,respectively, which may be produced by one color separation cube, e.g.,“X”-cube 204 in FIG. 2. FIG. 3B shows the wavelength spectra of anadditional set of three non-overlapping primary colors having spectralranges of approximately 450-520 nm, approximately 520-620 nm, andapproximately 620-750 nm, respectively, which may be produced by anothercolor separation cube, e.g., “X”-cube 205 in FIG. 2. As shown in thedrawings, there is significant overlap between the spectra of each ofthe primary colors in FIG. 3A and at least one of the primary colors inFIG. 3B, and vice versa. For example, the spectrum at the bottom of FIG.3B partially overlaps, at different ranges, the two bottom spectra inFIG. 3A. It will be appreciated by persons skilled in the art that,despite the significant overlaps between primaries, the six spectralranges illustrated in FIGS. 3A and 3B represent six distinct primarycolors. According to embodiments of the invention, the specific colorchoices and partial overlap design of the primary color wavelengthranges shown in FIGS. 3A and 3B may result in a significantly widercolor gamut and image brightness, compared to prior art color displaydevices, as described below.

FIG. 4 schematically illustrates the resulting color gamut of theprimary color spectra of FIGS. 3A and 3B. As clearly shown in FIG. 4,the color gamut produced by a typical positive motion picture film iscompletely covered by the gamut of the six primary colors of FIGS. 3Aand 3B. As further shown in FIG. 4, the white point coordinates obtainedby the sum of all primaries are x=0.313 and y=0.329. The luminancevalues for the colors obtained by this configuration are in generalequal to or higher than the luminance values that can be obtained forthe same colors from a typical projection film, e.g. a positive motionpicture film. Thus, in general, all the colors that can be reproduced byprojection film can be reproduced by devices using the primary colorselections of FIGS. 3A and 3B, both in terms of color coordinates and interms of intensity. It should be appreciated that although the primarycolor selections of FIGS. 3A and 3B provide desirable results in termsof image color and brightness, there may be other suitable selections ofsix primary colors, with partial overlap, that provide similar (or evenbetter) results, in accordance with specific implementations.

Example 2 Multiple Primaries, Single Panel, Sequential Display

The following example illustrates implementation of the presentinvention in the context of a six-primary-color sequential display. In asequential display system, the colors are typically produced by asequential color switching mechanism, e.g. a color wheel 1304 as shownin FIG. 13 or a color drum, which transmits each color for a preset timeperiod (window) within each field of the video stream. In such a system,the relative intensities of the primary colors may be adjusted byadjusting the relative sizes of a plurality of color filter segments1306 (FIG. 13) on the color wheel. The single panel configuration, e.g.,a panel 1302 (FIG. 13), may be implemented with either LCoS (LiquidCrystal on Silicon) or micro-mirror (DMD™) type panels, which areavailable, for example, from Texas Instruments, U.S.A., as is known inthe art. In this example, the spectra of FIGS. 3A and 3B are produced bysix filter segments, wherein each filter segments transmit one of thespectra of FIG. 3A or 3B. The operation of multi-primary sequentialprojection color displays is discussed in detail in the above-referencedInternational Applications.

For a multiple-primary system, there may be numerous combinations ofcolor filters, having varying relative segment sizes, to produce adesired viewed color, e.g., a desired white color temperature. Therelative segment sizes of the color filters may affect the over-allbrightness of the display, e.g., relative to the utilized portion of thelight generated by the light source. The relative segment sizes of thecolor filters may also affect the relative intensity of each of theprimary colors. Thus, the relative segment sizes of the color filtersmay be selected to provide a desired, e.g., maximal, over-all brightnessof the display and/or a desired relative intensity of each of theprimary colors, for example, to optimize specific implementations, asdescribed below.

In order to calculate the reproducible color gamut, the light sourcespectrum, e.g. as shown in FIG. 1A or FIG. 1B, may be multiplied by atransmission spectrum (not shown) of the optical engine used, e.g., thesingle panel DMD™ type optical engine. Such multiplication may excludethe influence of the color generating elements, e.g., the color filters.The resulting spectrum may then be multiplied by the transmissionspectra of the color filters to provide a set of primary reproduciblespectra corresponding to the primary colors, respectively. As is knownin the art, CIE 1931 x and y values of the color points corresponding tothe primary reproducible spectra may be calculated to determine thereproducible color gamut. The relative segment sizes of the colorfilters may be selected according to the primary reproducible spectra,so as to provide a maximal over-all brightness, e.g., when all theprimary colors are at their maximum levels, and to provide a desiredrelative intensity for each primary color.

Example 3 Five Primaries, Single Panel, Sequential Display

It should be noted that the use of six primary colors is advantageousbecause six primaries may provide more flexibility in color adjustmentcompared to systems using less than six primaries. However, according tosome embodiments of the invention, there are certain advantages in usingless than six primary colors. One such advantage is that more time canbe allocated to each primary in a sequential projection system, therebyimproving the temporal resolution (bit depth) of the displayed image.According to this embodiment of the invention, five primary colors maybe used. For example, the five primaries may include a blue color havinga wavelength spectral range from about 400 nm to between 460 nm and 540nm, a cyan color having a spectral range from between 400 nm and 460 nmto between 500 nm and 560 nm, a green color having a spectral range frombetween 480 nm and 520 nm to between 540 nm and 580 nm, a yellow colorhaving a spectral range from between 500 nm and 550 nm to 650 nm ormore, and a red color having a spectral range from between 580 nm and620 nm to 700 nm or more.

FIG. 5 schematically illustrates transmission spectra for five filtersegments that may be used by a five-primary-color display in accordancewith embodiments of the invention. The filter selections of FIG. 5 mayenable reproduction of a color gamut that is slightly wider than thestandard NTSC color gamut, especially in the yellow-red regions, e.g.,the yellow-red colors that can be displayed by this system may be moresaturated than those allowed by the standard NTSC gamut, as shownschematically in FIG. 6. In order to balance the white point with allprimaries fully transmitted, as described above, the relative segmentsizes of the blue, cyan, green, yellow and red primaries in this exampleare 0.8, 0.8, 0.6, 1.1 and 1.7, respectively. This configuration mayallow a brightness gain of about 40 percent over the six-primary colorwheel configuration described above with reference to the primary colorselections of FIGS. 3A and 3B. Furthermore, the brightness of a displaydevice using the five primary color filter selections of FIG. 5 mayproduce image brightness about 1.9 times higher than the imagebrightness of a three-primaries (e.g., RGB) projection display usingNTSC primary colors (with relative sizes of 0.5, 1, and 1.6 for theblue, green and red color filter segments, respectively). According tothese embodiments, the increase in brightness may be achieved byincreasing the amount of overlap between the transmission spectra of thedifferent color filter segments, resulting in a slightly narrower colorgamut than the six-primary color gamut shown in FIG. 4

Another possible application of multiple primaries is for significantlyincreasing the brightness of a device producing the color gamut of aconventional REC-709 or similar display. FIG. 7 schematicallyillustrates filter transmission curves according to this embodiment ofthe invention. The filter segments in this example are used withrelative segment sizes of 1, 0.9, 0.4, 1 and 1.7 for the blue, cyan,green, yellow and red primary color filter segments, respectively. Theresulting color gamut of this embodiment is illustrated schematically inFIG. 8. It will be appreciated that the color gamut produced in thisexample is still larger than the REC-709 color gamut, particularly inthe yellow and cyan regions. However, the brightness that may beachieved by this display is about 40 percent higher than the brightnessof a corresponding display using only the standard REC-709 RGB filters(with relative segment sizes of 0.8, 0.7, 1.5 for the blue, green andred primary color filter segments, respectively).

Example 4 Four Primaries, Single Panel, Sequential Display

In some embodiments of the invention, a four primaries display may alsoprovide many advantages for the multi-primary color display. Accordingto these embodiments, improved brightness may be achieved by theaddition of a yellow primary color filter segment to the RGB segments.White balance may be achieved by adjusting the relative segment sizes,as described above. For example, the four primary colors may include ablue color having a wavelength spectral range from about 400 nm tobetween 460 nm and 540 nm, a green color having a spectral range frombetween 480 nm and 520 nm to between 540 nm and 580 nm, a yellow colorhaving a spectral range from between 500 nm and 550 nm to 650 nm ormore, and a red color having a spectral range from between 580 nm and620 nm to 700 nm or more.

FIG. 9 schematically illustrates transmission curves of four primarycolor filter segments that may enable the device to produce a gamutcomparable to the NTSC standard gamut, as schematically illustrated inFIG. 10, which is similar to the five-primary color gamut shown in FIG.6. White balance may be achieved, as described above, by using relativesegment sizes of 1.2, 0.8, 1 and 1 for the blue, green, yellow and redprimary color filter segments, respectively. This configuration mayresult in an image brightness gain of about 90% over the brightnesslevel of a white-balance-corrected NTSC RGB color gamut (with relativesegment sizes of 0.6, 1 and 1.5 for the blue, green and red primaries,respectively), i.e., the brightness gain in this example is similar tothe brightness gain of the five-primary color display described above.

In other embodiments of the invention, a four-primary color display maybe used to increase the brightness of an REC-709 gamut by adding ayellow primary color filter segment. The filters transmission curves forthis alternate embodiment are schematically illustrated in FIG. 11. Thespectral ranges of FIG. 11 may be wider than the spectral ranges of FIG.9 in order to reproduce a wider color gamut. The relative sizes of thecolor filter segments used in this example are 1.5, 0.7, 1.2 and 0.9 forthe blue, green, yellow and red primary color filter segments,respectively. The resulting color gamut of this example is schematicallyillustrated in FIG. 12. It will be appreciated that this gamut is stilllarger than the REC-709 color gamut, particularly in the yellow regions,as shown in FIG. 12. The brightness that may be achieved by this displayis about 50 percent higher than the brightness of a display using onlythe REC-709 RGB color filter segments (with relative segment sizes of0.8, 0.7, 1.5, for the blue, green and red primary color segments,respectively).

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1-20. (canceled)
 21. A display device to produce a color image, the device comprising a color filtering mechanism to sequentially produce light of at least four non-white colors by transmission through at least four non-white color filters respectively, each color filter having a relative segment size, wherein the relative segment size of at least a first of said non-white color filters is greater than the relative segment size of at least a second of said non-white color filters.
 22. The device of claim 21, wherein said color filtering mechanism comprises a plurality of filter segments on a color wheel.
 23. The device of claim 21, further comprising a light source.
 24. The device of claim 21, further comprising a spatial light modulator to produce said color image by modulating light filtered by said color filtering mechanism.
 25. The display device of claim 21, wherein said at least four color filters comprise a blue color filter, a green color filter, a yellow color filter, and a red color filter, wherein the blue color filter has the greatest relative segment size, and wherein the green color filter has the smallest relative segment size.
 26. The display device of claim 21, wherein said at least four color filters comprise at least five color filters.
 27. The display device of claim 26, wherein said at least five color filters comprise a blue color filter, a green color filter, a yellow color filter, a red color filter, and a cyan color filter, wherein the red color filter has the greatest relative segment size, and wherein the green color filter has the smallest relative segment size.
 28. The display device of claim 27, wherein said yellow color filter has greater relative segment size than each of the blue and cyan color filters.
 29. The display device of claim 28, wherein said blue color filter has greater relative segment size than the cyan color filter.
 30. A method of producing a color image, the method comprising sequentially transmitting light of at least four non-white colors corresponding to said color image through at least four non-white color filters respectively, each color filter having a relative segment size, wherein the relative segment size of at least a first of said non-white color filters is greater than the relative segment size of at least a second of said non-white color filters.
 31. The method of claim 30, wherein sequentially transmitting light of said colors comprises sequentially filtering light of an illumination unit.
 32. The method of claim 30, wherein said at least four color filters comprise a blue color filter, a green color filter, a yellow color filter, and a red color filter, wherein the blue color filter has the greatest relative segment size, and wherein the green color filter has the smallest relative segment size.
 33. The method of claim 30, wherein said at least four color filters comprise at least five color filters.
 34. The method of claim 33, wherein said at least five color filters comprise a blue color filter, a green color filter, a yellow color filter, a red color filter, and a cyan color filter, wherein the red color filter has the greatest relative segment size, and wherein the green color filter has the smallest relative segment size.
 35. The display device of claim 34, wherein said yellow color filter has greater relative segment size than each of the blue and cyan color filters.
 36. The display device of claim 35, wherein said blue color filter has greater relative segment size than the cyan color filter. 